Quantum Effects and Phase Tuning in Epitaxial Hexagonal and Monoclinic MoTe₂ Monolayers

Abstract

Monolayer (ML) transition-metal dichalcogenides exist in different phases, such as hexagonal (2H) and monoclinic (1T') structures. They show very different properties: semiconducting for 2H-MoTe₂ and semimetallic for 1T'-MoTe₂. The formation energy difference between 2H- and 1T'-phase MoTe₂ is small, so there is a high chance of tuning the structures of MoTe₂ and thereby introducing applications of phase-change electronics. In this paper, we report the growth of both 2H- and 1T'-MoTe₂ MLs by molecular-beam epitaxy (MBE) and demonstrate its tenability by changing the conditions of MBE. We attribute the latter to an effect of Te adsorption. By scanning tunneling microscopy and spectroscopy, we reveal not only the atomic structures and intrinsic electronic properties of the two phases of MoTe₂ but also quantum confinement and quantum interference effects in the 2H- and 1T'-MoTe₂ domains, respectively, as effected by domain boundaries in the samples.